spi peripheral doesn't work if MISO pin set to -1

pataga
Posts: 38
Joined: Sat Aug 12, 2017 5:53 am

spi peripheral doesn't work if MISO pin set to -1

Postby pataga » Sun Jul 07, 2019 10:33 am

Hi, I'm using the hspi peripheral to write to an LCD - so I only need the SCK and MOSI pins on the spi peripheral (am using software SS).

I'm using the esp32-hal api : when I set the MISO pin set to -1, there is no compilation error, and no run-time error, but the spi transfers do not work. If I set the MISO pin to an unconnected i/o pin, no problem, the LCD display works fine.

But my problem is I am pin constrained on my real application - I don't have any spare unused pins that I can use for MISO.

So is this a software or hw issue ? Any workarounds ? From googling i see that even input only pins can't be used for MISO.

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